1. Field of the Invention
The present invention relates to a method and device for controlling a headrest of an automotive seat so as to move the same to a non-use position where it is lowered away from the view field of an occupant on the seat, thereby enabling him or her to attain a good view over the seat back.
2. Description of Prior Art.
There has been known a movable headrest for an automotive seat, which is moved by a motor under a switching control, so that the headrest body may adjustably be displaced to a use position upon the top of the seat back, where the headrest body erects thereon to readily support the head of an occupant sitting on the seat, or to a non-use position where the headrest body is located away from the forward view field of another occupant sitting on the other seast. Conventionally, in this sort of headrest device, an automatic operation switch is provided for effecting such headrest displacement with one-touch operation, and therefore, a driver on a front seat can operate this switch to cause a headrest on a rear seat to rotate forwardly below his or her backward sight line, to attain a good backward view field over the rear seat and further, an occupant sitting on the rear seat can cause the same displacement of a headrest on the front seat to a point below the forward sight line, by operation of the automatic operation switch, to secure a good forward view field over the front seat. On the other hand, the headrest body can be returned from that non-use position to the use position, through one-touch switching operation of the automatic switch.
According to this ordinary movable headrest device, the movable range of the headrest body between the use and non-use positions is limited by two associated limit switch, one of which is for limiting the movement of the headrest body to the use position and the other of which is for limiting that of the headrest body to the non-use position. Further, a manual adjustment switch is provided to enable adjustment of the headrest body in height and fore-and-aft positions, and thus includes a height adjustment switch area connected electrically with its associated motor and adapted for energizing the motor to drive for height adjustment of the headrest body, and a fore-and-aft adjustment switch area connected likewise with its own motor and adapted for energizing the motor to drive for adjusting forward and backward positions of the headrest body relative to the seat back. As such, the headrest movement control has been found advantageous in easily displacing the headrest body between the use and non-use positions, as well as enabling vertical and horizontal adjustments of the headrest, as desired, with respect to the seat back.
However, this prior art has been with such drawback that a move range limit is only given to the headrest displacements between the use and non-use positions by way of the foregoing two limit switches, which means that such limit is not applied to the adjusting movements of the headrest body in the fore-and-aft directions which is effected by the manual adjustment switch. As a result, during the fore-and-aft adjustment, if the manual adjustment switch is kept turned on, the headrest body continues to move until it is stopped by the limit switch, raising thus the possibility that the headrest body might damage or injure an occupant on the seat, and making the occupant nervous about the movements of the headrest body.
The conventional headrest device and its related control method, in addition to the above drawback, has been found defective in having no idea as to the variation of movement speed of the headrest body in the course of displacing it between the use and non-use positions as well as adjusting the its fore-and-aft positions. In other words the respective motors for those two operations are unchangeable or fixed in rotation rate, and consequently it is impossible to offer a desirable rapid displacement of the headrest body between the use and non-use positions and slow speed for making easy the fine adjustments of the headrest body by operating the manual adjustment switch.